Trades shows across all markets, not just photography, are becoming obsolete just due to youtube and the internet. In a rather quick period in time, you can learn everything you need to know about a particular product and/or future product releases. Although it would be nice to get the item in your hands before buying, you dont really need to go to a trade show for that anymore either.
With cameras, especially the high end ones, you can visit a dealer for a test drive. Now I know not everyone can easily get to a dealer for some of this gear, but then again not everyone can get to NYC for Photo Plus either. But if you can get to NYC, regardless of the time of year, you will be able to visit a dealer on your schedule.
On top of that, as a professional who shots things besides events and weddings, Photo Plus stopped catering to us years ago. All of these gadgets really serve us no purpose and most pros just look at them as something to waste money on.
On top of this, rates have been going up at the Javits center pretty drastically, pushing vendors out. This is why there are so many events away from the Center, just due to the huge cost of having a booth. The real reason Photo Plus may be declining could be the Javits Center
